Project Summary Taste perception plays a key role in diet selection. Although bitter compounds are often associated with toxic substances, a large number of nutritionally significant food sources contain bitter phytochemicals (e.g., broccoli, spinach). Understanding how bitter taste is perceived and detected is of great importance for increasing the acceptability of pediatric medicines and may assist in efforts to promote healthy eating in children and adults. Under normal feeding and drinking conditions, taste compounds mix with saliva before reaching their receptor targets. Little is known about how the proteins in saliva interact with taste stimuli and alter bitter taste perception. Salivary protein composition changes with exposure to bitter diets (the induction phase) and in turn alters the behavior of animals consuming bitter diets by increasing the acceptability of their taste (the increased acceptance phase). Although there is a strong link between bitter diets and salivary protein (SP) expression, the physiological mechanisms underlying these linkages are unknown Specific Aim 1 will examine the induction phase by examining the role of taste in the upregulation of SPs. Specific Aims 2 and 3 will examine the increased acceptance phase. We hypothesize that SPs will diminish taste- mediated responses at two levels of organization: 1) immediate behavioral responses, as assessed by taste reactivity tests; 2) calcium responses of isolated taste cells to chemical stimuli. Specific Aim 4 will examine the role of SP profile in diet acceptance. We hypothesize that diets that induce similar patterns of expression will increase acceptance of each other, while diets with different patterns will not. These experiments will allow us to identify which proteins are important for the increased acceptance of bitter diets.